JP4827334B2 - Radio call handover between systems that support circuit call and packet call models - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to communication systems, and more particularly to systems and methods for supporting wireless call handover between wireless communication systems and components thereof that support different call models, including line and packet call models.
[0002]
[Prior art]
Because an important feature of many wireless communication systems is mobility, users involved in calls are supported by a second set of wireless infrastructure equipment from a first location supported by the first set of wireless infrastructure equipment. The call can be moved to the second location without much interruption. Many early wireless communication systems were developed to provide mobile phone services. Early cell phone systems typically employed a single radio base station with limited capacity but arranged to cover a large geographic area. The mobile user can move widely within the coverage area and expect the call to be maintained under the condition that the user does not move to a location where the radio frequency path to the base station is unavailable I was able to. When cellular cellular telephone systems with multiple radio base stations each serving a much smaller adjacent area, or “cell”, were developed, the user involved in the call would be able to cover the system without interrupting the call. It was extremely important to be able to move from cell to cell through the area.
[0003]
Functions and implementations that allow a second radio base station to service a stable call currently served by the first radio base station (or another similar element of a radio system that provides a radio interface) The process is called “handoff” or “handover”. Initially, handover was provided between single system and similar technology cells. However, a standard protocol has been developed that allows handover between cells of different systems and allows handover between cells and / or systems of different technologies. For example, a standard protocol allows a user to maintain a call as it crosses the boundary from one radio system to another radio system, possibly with different entities operating and using different types or brands of infrastructure equipment. become. For example, this type of protocol includes ANSI-TIA / EIA41-D published by the American National Standards Institute, a standard intersystem operating protocol known as Cellular Radiotelecommunications Intersystem Operations, and GSM09.02 Mobile published by the European Telecommunications Standards Institute (ETSI). There is an Application Part (MAP) protocol. Furthermore, standard protocols have also been developed to allow handover between systems / cells of different (but collaborative) air interface technologies that use the same call model. For example, a subscriber's handset and system infrastructure equipment performs a call handover from a cell employing a digital transmission technology such as CDMA or TDMA to a cell employing an analog transmission technology such as AMPS. be able to. The performance of performing handover between the GSM system and the UMTS system has also been described. Historically, the need for mobility has been a motivation for using handover, but handover can improve load reliability and improve reliability, even in applications that do not require mobility. It can provide important functionality.
[0004]
Existing wireless communication systems that provide handover employ a circuit call model. As used herein, the term “call” refers to an information transfer session between terminal sets over a communication system or network, and is a classical line voice call, packet voice call, line data call, connectionless call, or It is intended to include, but is not limited to, packet data calls and multimedia variants thereof. The term “line” as applied to a call refers to an information transfer mode that occurs between endpoints defined via reserved network resources and in which the data units are not individually addressed. Once a path or route is established for a line call, no further routing or addressing is required. It will be appreciated that some components that carry circuit calls may be implemented using packet-based technology or cell-based technology. The term “packet” as applied to a call refers to an information transfer mode in which the information stream is divided into packets or units and each packet or unit is individually addressed. Packet calls do not necessarily have to secure network resources. The term “call model” refers to the procedures, states, and state transitions necessary to set up, maintain, modify, and terminate a call. The line call model is a call model used to establish and control a line call. Examples of known line call models include ITU-T signaling system No7, ANSI-41, ANSI-136, ANSI-95, and GSM04.08. The packet call model is a call model used to establish and control a packet call. Examples of known packet call models include IETF RFC-2543 (Session Initiation Protocol (SIP)) and ITU standard H.323.
[0005]
New communication systems, including wireless systems, that employ a packet call model have been proposed or developed. The packet call model allows specific resources and equipment to be allocated to carry bearer traffic for the call as needed while on the phone, and the specific resources and equipment used are for each packet. Implies that it can be made variable. The packet system can support end-to-end packet calls, ie calls where each terminal is adapted for packet communication and the call is carried over a packet network. However, because most of the world's communications infrastructure employs line technology, many packet systems use existing line networks to interwork calls at least on certain well-defined interfaces. It is designed as follows. Thus, a call may originate from a packet terminal but terminate at a line terminal, or vice versa. Systems that connect calls between conventional landside packet and circuit networks are known in the art, and such systems are known as Lucent Technologies (Murray Hill, New Jersey, USA) under the name PACKETSTAR Voice Gateway. ) Is sold by.
[0006]
New packet radio systems are expected to be built in stages, and such systems may first be developed to overlay existing line radio systems where system operators have made significant investments. high. Therefore, it is desirable to provide handover between the packet system and the circuit system for appropriately equipped subscriber handsets and other terminals. Such a handover advantageously provides service to subscribers at a location where a new packet system is available, and the packet system is unavailable or temporarily lacks capacity. The location can be serviced to the subscriber by the existing line system. In addition to providing mobility, handover between these systems can balance the load and improve reliability.
[0007]
However, existing line systems have adopted network topologies and handover processes that are only suitable for line call models. In particular, commercially deployed circuit systems employ anchor mobile switching centers or “anchor MSCs” to control calls throughout their duration. The anchor MSC is generally the first MSC with substantial control over the call. While making a call, even if the user moves to another system coverage area, typically controlled by a different MSC, other specific functions are controlled by the anchor MSC and bearer traffic for the call. Are routed through the anchor MSC. The current serving MSC controls the handoff.
[0008]
The topology of the packet radio system differs considerably from that of existing circuit radio systems according to the proposed standards. In particular, in the proposed packet radio system, the system elements that provide the control function can be different from the system elements that provide the switching function, the transmission function, and the vocoder function. Packet radio systems do not employ anchor MSC components. Further, the packet radio network employs both line and packet call models to interface with other networks, while the line radio network employs only the line call model. These significant differences and others make it impossible to directly apply the traditional handoff process developed for line wireless networks to new packet networks.
[0009]
In addition, existing line networks employ a technology that represents a significant investment for each operator, but cannot be upgraded without major replacement or substantial additional investment. Therefore, any handover process and functionality developed for packet systems to support handovers with existing line radio systems as appropriate, minimizes the changes or upgrades required for existing line radio systems. Must. Thus, handoff procedures developed for homogeneous packet networks do not satisfy use in packet systems that must support handover with circuit systems.
[0010]
[Problem to be Solved by the Invention]
Accordingly, it is an object of the present invention to provide a system and / or method for performing a handover in a wireless system that avoids the above disadvantages of the prior art.
[0011]
[Means for Solving the Problems]
In a preferred embodiment constructed in accordance with an aspect of the present invention, a wireless network includes a packet radio system configured to interoperate, including support for handover, using a defined interoperability protocol, and a circuit radio system. Including. The line radio system is of conventional design and may use any suitable radio technology or standard. The circuit radio system includes at least one base station and at least one mobile switching center (or equivalent element).
[0012]
A packet radio system can be constructed in a manner generally similar to known packet radio networks, but adds certain components to provide internal call model handover functionality in accordance with an aspect of the invention, and other Change the component. For example, in the packet radio system, the basic structure and functionality of the General Packet Radio Service (GPRS) supplemented by the IP Multimedia Subsystem (IM) described in the Third Generation Partnership Project (3GPP) are changed as appropriate. It can be employed as it is. Alternative packet radio system technologies can also be used. When using a packet radio system that employs a GPRS-like architecture, the packet system includes a set of interconnected at least one of the following GPRS elements. A base station, a radio network controller, a serving GPRS support node (SGSN), and a gateway GPRS support node (GGSN). These elements generally operate as in GPRS systems with some modifications to implement the interoperable handover function of the present invention. The packet system also includes an interconnected set of at least one of the following elements from the 3GPP IM subsystem. Call state control function (CSCF), media gateway (MG), and media gateway control function / transmission signaling gateway (MGCF / T-SGW), which are interconnected with other elements. The CSCF is a network element that implements the network function of the packet call model. The MG converts bearer content between the encoding and transmission format used in the packet network and the encoding and transmission format used in the circuit network. For example, in the case of a voice call, the MG can perform a vocode function that converts between a compression format used in a packet network and a PCM format used in a circuit network. The MG can also convert between formats used in heterogeneous packet networks. The MGCF / T-SGW controls the MG and provides a control interface to the external network. The MGCF / T-SGW is also used to emulate a specific function of the anchor MSC when inter-system operation using a line radio network is required.
[0013]
According to aspects of the present invention, four possible handover situations are supported.
A stable call that terminates on the circuit landside network and initially uses the packet radio system can be handed over to the circuit radio system. Because existing line systems require an anchor MSC to maintain call control throughout its duration, the MGCF / T-SGW, MG, and CSCF cooperate to emulate the function of the anchor MSC. This looks just like another line radio system to the line radio system. After the handover, bearer traffic from the circuit radio system is routed to the circuit landside network through the MG. “Landside network”, as used herein, is intended to encompass any other network that provides an interface equivalent to a landside network, including but not limited to other wireless networks and transit networks.
[0014]
A stable call that initially terminates in the circuit landside network and initially uses the circuit radio system can be handed over to the packet radio system. In existing line systems, the anchor MSC is required to maintain call control throughout its duration, so the line system MSC maintains call control. The MGCF / T-SGW, MG, and CSCF cooperate to emulate the functionality of the circuit MSC for intersystem handover. This looks just like another line radio system to the line radio system. After the handover, bearer traffic exchanged between the packet radio network and the circuit landside network is routed to the circuit radio system through the MG.
[0015]
A stable call that terminates on the packet landside network and initially uses the packet radio system can be handed over to the circuit radio system. Because existing line systems require an anchor MSC to maintain call control throughout its duration, the MGCF / T-SGW, MG, and CSCF cooperate to emulate the function of the anchor MSC. This looks just like another line radio system to the line radio system. Before handover, the MG may or may not be a bearer path element. After the handover, bearer traffic from the circuit radio system is routed to the packet land side network through MG and GGSN.
[0016]
A stable call that terminates on the packet landside network and initially uses the line radio system can be handed over to the packet radio system. Such a call must pass through the network connection function and masks the presence of the packet network with respect to the circuit network. Therefore, this case is reduced to the example of a call that terminates on the circuit landside network and uses the circuit radio system for the first time and is handed over to the packet radio system.
[0017]
These four handover situations described all possible handover combinations between the packet network and the circuit network. The systems and methods disclosed herein advantageously enable inter-system handoff between packet radio systems and conventional circuit radio systems. Handoff functionality is provided to the packet system that minimizes or avoids the overall need to modify or upgrade existing circuit systems.
[0018]
These and other features of the present invention will be best understood from the following detailed description of the preferred embodiments of the invention, taken in conjunction with the accompanying drawings.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
1-6 are block diagrams illustrating a preferred embodiment of a collaborative wireless network 100 constructed in accordance with an aspect of the present invention.
[0020]
The present application relates to communication systems. In the communications field, various signal leads, buses, data paths, data structures, channels, buffers, and other communication paths can be used to implement facilities, structures, or methods that convey information or signals, and these You will find that they are often functionally equivalent. Thus, unless stated otherwise, references to devices or data structures that convey signals or information generally refer to all functionally equivalent devices and data structures.
[0021]
As best shown in FIGS. 1-6, connections between elements are called links or paths and are shown as solid or wavy lines. Such lines may or may not have a reference number applied to them, and are further marked with a single hash mark, double hash mark, feature mark such as dot or "X" applied to it. There are also things. Line connections without reference numbers or other markings represent links available for carrying control or bearer traffic, which may or may not be used in the particular situation shown in the figure. A solid line to which no feature mark is added represents a link carrying bearer information. A wavy line without a feature mark represents a link carrying control information. The connection of lines with reference numbers and the above-mentioned feature marks (hereinafter referred to as “paths”) is provided as an overlay to identify the links that are actually used among the available links in the specific situation shown in the figure. ing. Thus, the path does not indicate additional links, but indicates whether to use available links and how to use available links.
[0022]
1-6 illustrate the structural organization of the network 100, as well as the initial and final configuration of control and bearer paths before and after several different handover situations supported in a preferred embodiment of a communication system constructed in accordance with the present invention. Is further shown. A path with a single hash mark indicates the initial configuration of the bearer path before handover. The path with the double hash mark indicates the final configuration of the bearer path after the handover. The dotted path indicates the initial configuration of the control path before the handover. The path with “X” indicates the final configuration of the control path after the handover.
[0023]
As best shown in FIG. 1, a network 100 and a line radio communication system are configured for inter-system operation and are also configured to connect to an appropriate landside network. 120. As used herein, the term “landside network” is intended to encompass any other network that provides an interface equivalent to a landside network, including but not limited to other wireless networks and transit networks. For example, a packet radio system 110 is shown in FIG. 1 connected to a public switched telephone network (PSTN) 132, which can be generally characterized as a circuit network, and a packet data network 136, which can be generally characterized as a packet network. . As best shown in FIGS. 3 and 4, circuit radio system 120 may also connect to external network 132. Although networks 132 and 136 may actually employ various circuit and / or packet technology transmission and switching elements, networks are herein employed by other networks and systems, and in particular by each network. Characterized according to the interface presented in the call model.
[0024]
As used herein, the term “call” refers to an information transfer session between terminal sets over a communication system or network, and is a classical line voice call, packet voice call, line data call, connectionless call, or Including but not limited to packet data calls and multimedia variants thereof. Although this application refers to a call involving two terminals, those skilled in the art will understand how to modify the exemplary embodiment to support multiple joint calls in light of the spirit of the present invention.
[0025]
As is known in the art, network 110 conforms to IETF RFC-2543 (Session Initiation Protocol (SIP)) and ITU standard H.264. Any suitable packet protocol, including those specified in H.323, may be used to interface with the packet landside network 136 (hereinafter referred to as “PDN”). Other protocols and standards can be used. The network 110 can interface with the line landside network 132 using a line protocol commonly known in the art as ITU-T signaling No. 7. As will be further described, the packet radio network 110 includes a format and call model required by the packet radio network, and a format and call model required by the circuit landside network 132 (hereinafter referred to as “PSTN”). Appropriate gateway facilities 150 and 154 are preferably provided to convert bearer and control information between the two.
[0026]
Although an exemplary embodiment of the network 100 is illustrated as including a single packet radio system 110 and a single line radio system 120, those skilled in the art will recognize that a commercially developed embodiment is It will be understood that a plurality of each type of wireless system can be incorporated. Similarly, although an exemplary embodiment of network 100 is shown connected to two landside networks, namely PSTN 132 and PDN 136, a commercially developed embodiment is connected to several such networks. It will be understood that it is possible. Most commercial wireless systems incorporate multiple connection points to interface to other wireless systems and external, public, or landside networks.
[0027]
Line radio system 120 is preferably any suitable radio communication system. For example, system 120 may be any of the wireless system types commonly known as (but not limited to) AMPS, GSM, TDMA, or CDMA, and the behavior of the system type may be known industry, government, or It is defined by the standard body between governments. Further, the system 120 preferably provides a well-defined interface for interoperability with other wireless systems. For example, system 120 is a protocol known as ANSI-TIA / EIA41-D: Cellular Radiotelecommunications Intersystem Operations published by the American National Standards Institute, the GSM 09.02 Mobile Application Part (MAP) protocol published by the European Telecommunications Standards Institute (ETSI), and A standardized intersystem operating protocol may be implemented, which is another suitable protocol.
[0028]
As best shown in FIGS. 1-6, circuit system 120 includes at least one base station system (BSS) 122 having a control connection and bearer connection to at least one mobile switching center (MSC) 124. Is preferred. As best shown in FIGS. 3 and 4 (but not shown in other figures for clarity), the MSC 124 has a control connection and a bearer connection to the landside network PSTN 132. The MSC 124 may also have a control connection and bearer connection (not shown) to the PDN 136 via an internetwork gateway. When a call terminates at the PDN 136 via the interworking gateway, the interworking gateway masks the packet nature of the PDN 136 so that the circuit system 120 handles the call in the same way as a call that terminates at the PSTN 132. . The MSC 124 preferably has a control connection and a bearer connection to the media gateway element 150 (described in more detail below) of the packet network 110. For simplicity, only a single BSS and a single MSC are shown. However, in commercial embodiments, the system 120 is likely to incorporate a large number of BSSs connected to the MSC and may incorporate several MSCs. System 120 is not necessary for an understanding of the present invention and may include other elements that are omitted for the sake of clarity.
[0029]
The packet radio system 110 can be constructed in generally the same manner as known packet radio networks, but with the addition of certain components and others to provide an interoperable handover function according to one aspect of the invention. The component has been changed. This will be further described later. For example, the system 110 can employ the basic structure and functionality of the general packet radio service (GPRS) with further modifications as will be described later. GPRS is described in an extended series of standards documents including the European Telecommunications Standards Organization GSM Standards 02.60, 03.60, and 04.60 and the Third Generation Partnership Project (3GPP) Technical Specification 3GPP TS 23.060 A packet radio communication system. The following description of packet radio system 110 uses GPRS terminology, but is partly an implementation of a mobile IP system as defined in RFC 2002, 2003, 2004, 2005, 2006, and 2344 (Internet Technical Standards Committee). (IETF: Internet Engineering Task Force)), other packet radio systems including but not limited to the CDMA packet system defined in ANSI standard IS-835 may be employed.
[0030]
As best shown in FIGS. 1-6, the system 110 preferably includes a base station system (BSS) 142, a serving GPRS support node (SGSN) 146, a gateway GPRS support node (GGSN) 148, a media gateway (MG). 150, a call state control function (CSCF) 152, and a media gateway control function (MGCF / T-SGW) 154. The BSS 142 is intended for wireless communication using suitable wireless user terminals 140a-140f (140 when referred to in a general context unrelated to a particular one of the handover situations of FIGS. 1-6). Has been adapted. The BSS 142 has a control connection and a bearer connection to the SGSN 146. SGSN 146 has a control connection and bearer connection to GGSN 148. The GGSN has a control connection and bearer connection to the MG 150. The GGSN 148 also has control and bearer connections to the landside network PDN 136 and may have such connections to other networks (not shown). The MG has a bearer connection to the landside network PSTN 132 and may have such a connection to other networks (not shown). GGSN 148 also has a control connection to CSCF 152. The MG 150 further has a control connection to the MGCF / T-SGW 154. CSCF 152 further has a control connection to MGCF / T-SGW 152. The MGCF / T-SGW 152 has a control connection to the PSTN 132.
[0031]
In general, BSS 142, SGSN 146, and GGSN 148 perform functions that are equivalent to the functions that they normally perform in a GPRS system. However, packet radio system 110 must also interoperate with circuit landside networks such as PSTN 132 and circuit radio systems such as system 120. Since the call model, control information format, and bearer content format used in the circuit system are different from those used in the packet system, the packet network 110 uses a bearer content or control message format specific to the packet network. It cannot communicate directly with the line network. Accordingly, the MG 150 performs the function of converting bearer content between the format used in the packet network 110 and the format used in the PSTN 132 and the line network 120. The MGCF / T-SGW 154 controls the MG 150. The MGCF / T-SGW 154 and CSCF 152 cooperate to convert call model and call processing related control information between the format used in the packet network 110 and the format used in the PSTN 132 and the circuit radio network 120.
[0032]
Further, MGCF / T-SGW 154 and CSCF 152 further cooperate to emulate the mobile switching center (MSC) handover function and anchor mobile switching center (anchor MSC) feature control function of the circuit radio network, thereby enabling the packet network. It is possible for the packet network 110 to interoperate with the line network 120 as if it were just another line network. The functionality required for the anchor MSC emulated in the packet system 110 is less than the full functionality required for the MSC in the line system 120. In particular, the emulated anchor MSC must manage handovers between systems, but does not need to manage radio resources. This is because in the packet system 110, radio resources are managed by the BSS 142 rather than the central MSC. The functionality of the emulated anchor MSC is mainly in the CSCF 152 and MGCF / T-SGW 154, and preferably has the ability to send handoff requests or return handoff related information to the MSC 124 of the circuit system 120. Including.
[0033]
Various functions required to support inter-system handover can be assigned to suit the particular architecture used to implement the packet system 110. In a preferred embodiment of a packet system 110 constructed in accordance with the present invention, the assignment may be as follows: The MG 150 performs all necessary conversion of bearer information for any call associated with both the wireless packet system 110 and either the line system 120 or the line landside network PSTN 132. The MGCF / T-SGW 154 converts a signaling protocol between the packet system 110 and either the line system 120 or the line landside network PSTN. The MGCF / T-SGW 154 also provides MG 150 via appropriate control messages including when to convert between bearer formats, instructions to the MG about which conversion to perform, and identification of the specific equipment to use. To control. The CSCF 152 implements a call model that is expected to be recognized by the circuit MSC during handover.
[0034]
Advantageously, in this manner, the changes or upgrades required for the circuit system 120 to interact with the packet network 110 are minimal or zero. It may be advantageous for the line system 120 to identify which user terminals 140 are capable of packeting and only attempt to hand over such terminals to the packet system 110. Most conventional line systems 120 include the ability to distinguish among user terminals that have the ability to connect a call to a network with a particular other system. For example, some user terminals transmit “class marks” that identify systems in which they can operate. Some wireless systems are also configured to negotiate with the user's home system for specific profile information that can identify the systems on which the user terminal 140 can operate. Therefore, to identify the user terminal 140 capable of packetizing with respect to the line system 120, a currently reserved value of a parameter used by the system 120 is defined, and the current performance of the inter-network connection performance of calls with other line systems is defined. Can include performing. Nevertheless, changes in standards related to the interpretation of the line system and its class mark or profile information may be advantageous. Alternatively, when using “mobile assisted handover” to determine which cell is the handover target, the user terminal preferably reports only compatible cells. This eliminates the need for changes to the line system and related standards.
[0035]
As described above, the packet radio system 110 can also be implemented using the CDMA packet system technology defined in ANSI standard IS-835. In this case, the function of the BSS 140 is performed by the radio base station apparatus (BTS) of the CDMA packet system, and the functions of the SGSN 146 and the GGSN 148 are performed by the home agent and the packet data serving node (PDSN) of the CDMA packet system.
[0036]
1 to 6 show an initial configuration and a final configuration of a control path and a bearer path for four different handover situations in the network 100. 7-9 are flow diagrams illustrating the steps of a method for performing a handover in combination with the network 100 of FIGS. 1-6 and in conjunction with aspects of the present invention. Each handover situation will be described in conjunction with a diagram showing the initial and final signal path configurations and a diagram showing the corresponding handover method.
[0037]
1, 2, and 7 are directed to a call handover from the packet system 110 to the line system 120 with the landside termination passing through a line network such as the PSTN 132. Therefore, this handover situation considers a case where a stable call is established between the wireless subscriber terminal 140a and the landside subscriber terminal 134 through the packet radio system 110 and the line landside network PSTN 132. In this situation, and in all other situations discussed herein, it does not matter whether the call originates from the wireless terminal 140 or from the landside terminals 134,138. Further, for all handover situations discussed herein, the terminal is illustrated with specific media or content in the figure (eg, terminal 140a is illustrated as a voice handset and terminal 134 is a normal voice phone) These terminals may include any media or content type supported by the wireless system and the landside network, including but not limited to voice, video, facsimile, etc. it can.
[0038]
Although the present invention is not directed to initial call setup, the following steps will serve as background for understanding an exemplary call establishment process from wireless terminal 140a to landside terminal 134. .
(A) The terminal 140a registers with the packet system 110 and “discovers” the CSCF 152 (ie, becomes aware of the CSCF 152).
(B) If the terminal 140a is a session start protocol, Using CS 323 or another suitable packet call setup protocol, a message is sent to the CSCF 152 requesting a call to the landside terminal 134 that happens to be in the circuit network PSTN 132.
(C) Since the called endpoint is in the circuit network PSTN 132, the CSCF 152 transmits a control message indicating that the packet session is directed to the MG 150 to the GGSN 148.
(D) The MGCF / T-SGW 154 must send a control message to the MG 150 to instruct to receive the end of the packet call, convert the bearer content from or to 64 kbps PCM, and convert the PCM stream Specifies that the trunk should transmit to or from line network PSTN 132.
(E) The MGCF / T-SGW 154 converts the packet call model function into signaling suitable for the circuit network PSTN 132 (for example, ITU-T No7 signaling message), and transmits the signaling to the PSTN 132.
(F) The MG 150 bi-directionally converts bearer traffic between the packet system 110 and the circuit landside network PSTN 132.
[0039]
As a result of the above process, a stable call is established between terminal 140a and terminal 134, which is shown in FIG. As best shown in FIG. 1, a control path 170 exists between the terminal 140 a and the CSCF 152. An additional control path 172 extends between CSCF 152 and GGSN 148, and an additional control path 174 extends between CSCF 152 and MGCF / T-SGW 154. A control path 176 extends between the MGCF / T-SGW 154 and the MG 150. All the control paths are packets. In addition, a line control path 178 extends between MGCF / T-SGW 154 and PSTN 132 to allow MGCF / T-SGW 154 to exchange call setup and other signaling with the line network. A packet bearer path 180 extends between the terminal 140a and the MG 150. A line bearer path 182 extends between the MG 150 and the PSTN 132. The MG 150 functions as a vocoder and converts bearer traffic between the packet radio system and the line landside network PSTN 132.
[0040]
FIG. 7 is a diagram illustrating a case where a handover is performed from the packet system 110 to the line system 120 in the case of a call between the wireless terminal 140 and the landside line terminal 134 used in conjunction with the cooperative wireless network 100 of FIG. 7 is a flow diagram illustrating a method 700 according to an aspect of the invention. The method begins at step 710 where the system 110 determines that a handover is required and the acceptable handover target is a base station 122 in the circuit system 120. The determination can be made by the BSS 142 of the packet system 110 and reported to the CSCF 152, for example. Various techniques are well known in the art for determining when a handover is required and which of several potential handover targets is optimal. Different radio system technologies have taken different approaches to this problem. For example, handover is desirable because the quality of the current RF path between the terminal and the base station is poor, to achieve load balancing, optimization between neighboring cells, or for other administrative or policy reasons. The method of selecting an appropriate handover target includes the so-called “mobile” where the wireless terminal reports the signal strength measurements of transmissions from nearby base stations and the polling of nearby base stations for signal strength measurements of the wireless terminals. Assisted handover ”. In connection with the present invention, any handover decision technique suitable for the radio system technology of systems 110 and 120 can be used.
[0041]
In step 712, the CSCF 152 has the handover target in the circuit radio system 120, so when communicating with the system 120, the CSCF 152, MG 150, and MGCF / T-SGW 154 must cooperate to emulate the anchor MSC. Recognize that. In step 714, CSCF 152 and MGCF / T-SGW 154 cooperate to negotiate a handover with system 120 by formatting and initiating an appropriate handover message sequence exchange with MSC 124. If the system 120 uses the ANSI-41 intersystem operating protocol, the appropriate message sequence is: (a) a facility indication from the MGCF / T-SGW 154 to the MSC 124 of the circuit system 120 requesting a traffic channel in the target cell. Call (Facilities Directive Invoke), (b) Confirm radio resource reservation, identify such resources (for example, identification of authorized traffic channels), Facility instruction dialogue (Facilities from MSC 124 to MGCF / T-SGW 154) Directive Conversation) and (c) Mobile on Channel Indication from the MSC 124 to the MGCF / T-SGW 154 notifying that the handover of the wireless terminal has been successful. In step 716, the system 120 allocates radio resources to be used for call processing and informs the system 110 of the identification of such resources. The circuit system 120 establishes a path 280 for the call through the BSS 122, the MSC 124, and the MG 150. Since the call originated within the packet system 110, the system must emulate an anchor MSC, and the call must still be routed through the packet system. Accordingly, the call extends between MSC 124 and MG 150 via bearer path 282.
[0042]
In step 718, under the instruction from the packet system 110, the wireless terminal starts using the assigned target traffic channel. In step 720, the MSC 124 notifies the MGCF / T-SGW 154 and CSCF 152 that the radio terminal 140b (see FIG. 2) has been successfully handed over to the circuit system 120. In step 722, resources used by the call in packet system 110 are released. The bearer path 182 between the MG 150 and the PSTN 132 continues to be used. Depending on the implementation, the vocode required for the wireless system may be performed by the MSC 124 and may be performed by the MG 150. A vocode at MG 150 is preferred in that it preserves network resources. In addition to addressing the need to convert vocode / format, MG 150 can also incorporate switching fabrics and other equipment to provide the specific functionality normally provided by circuit MSCs. However, the MG 150 can implement a fabric and provide a function using a technology other than the conventional circuit technology. The method ends at step 724.
[0043]
FIG. 2 is a block diagram showing the final configuration of the control path and bearer path when the handover from the packet system 110 to the circuit system 120 is successfully completed. Bearer path 280 extends from wireless terminal 140b through BSS 122 and MSC 124. Bearer path 282 further extends from MSC 124 to MG 150 of packet system 110. When the call is carried in the packet network, the bearer path 182 between the MG 150 and the PSTN 132 previously used to carry the call is still in use. A control path 270 extends from the wireless terminal 140b to the MSC 124. A control path 272 extends from the MSC 124 to the MGCF / T-SGW 154 of the packet radio system 110. The control path 176 that extended from the MGCF / T-SGW 154 to the MG 150 remains in place, and so does the signaling control path 172 that extends from the MGCF / T-SGW 154 to the CSCF 152. The circuit signaling control path from MGCF / T-SGW 154 to PSTN 132 also remains in place. Therefore, CSCF 152, MGCF / T-SGW 154, and MG 150 cooperate to perform the anchor MSC function for calls that are currently widely handled by circuit system 120.
[0044]
FIGS. 3 and 4 are directed to a call handover from the line system 120 to the packet system 110 with the landside termination passing through a line network such as PSTN 132. Therefore, this handover situation considers a case where a stable call is established between the wireless subscriber terminal 140c and the landside subscriber terminal 134 through the line radio system 120 and the line landside network PSTN 132.
[0045]
In order to perform a handover, a stable call must be established from the wireless terminal 140c to the landside terminal 134. The configuration is best seen in FIG. A control path 370 exists between the terminal 140 c and the MSC 124. An additional control path 372 extends between the MSC 124 and the PSTN 132. All the control paths described above are lines. A line bearer path 380 extends between the terminal 140 c and the MSC 124. A line bearer path 382 extends between the MSC 124 and the PSTN 132.
[0046]
FIG. 8 is a diagram illustrating a case where a handover is performed from the line system 120 to the packet system 110 in the case of a call between the wireless terminal 140 and the landside line terminal 134 used in conjunction with the cooperative wireless network 100 of FIG. 7 is a flow diagram illustrating a method 800 according to an aspect of the invention. The method begins at step 810, where the circuit system 120 determines that a handover is required and the acceptable handover target is a base station 142 in the system 110. See also the description of the handover decision associated with step 710. In step 812, the MSC 124 determines that the handover target is in the system 110. The line system 120 does not necessarily have to realize that the system 110 is a packet system.
[0047]
In step 814, the line system 120 formats and initiates a message sequence to exchange with the MGCF / T-SGW 154 via the control path 480 (FIG. 4) to indicate interest in handover. The message sequence may be exchanged by the serving MSC 124 or an anchor MSC (not shown) if present in the call. The MSC can adopt the same protocol and procedure as when handing over to the circuit MSC. If system 120 is using an ANSI-41 inter-system operating protocol, handover negotiation may employ the message sequence described with respect to step 714 in the reverse direction (ie, from the line system to the packet system). . The message sequence is received at MGCF / T-SGW 154 and information related thereto is transmitted to CSCF 152. In step 816, radio resources used by the packet system 110 for call processing are allocated and notified to the line system 120. Packet system 110 establishes a path 490 for the call from BSS 142 through MG 150. Since the call originated within the circuit system 120, the packet system 110 must emulate the circuit MSC, and the call must still be routed through the circuit system MSC 124. In step 818, the circuit system 120 instructs the wireless terminal 140 to begin using the allocated traffic channel (or equivalent resource) of the packet system 110.
[0048]
In step 820, the CSCF 152 notices the call and identification of the wireless terminal 140d. The CSCF instantiates a packet call model. In step 822, the packet system establishes a bearer path 490 for the call to MG 150. As a result of this step, a packet session is established from the wireless terminal 140d to the MG 150. The call extends along bearer path 492 to MSC 124 of circuit radio system 120 (or another anchor MSC, if present). Due to the requirement that the anchor MSC maintain control of the call, the landside network facing the call leg remains in the circuit system 120.
[0049]
Following the handover, the provision of features requested by the user (to the extent available in the circuit system 120) continues to be managed by the MSC 124 of the circuit system 120 (or another anchor MSC if present). In step 824, the serving MSC releases resources previously allocated to the call to the extent that it is not required to support the connection between MG 150, MSC 124, and PSTN 132. The method ends at step 826.
[0050]
FIG. 4 is a block diagram showing the final configuration of the control path and the bearer path when the handover from the line system 120 to the packet system 110 is successfully completed. The bearer path 490 extends from the wireless terminal 140d through the BSS 142 to the MG 150. Bearer path 492 extends further from MG 150 to MSC 124, thus allowing packet system 110 to route the call to the anchor MSC of circuit system 120. The bearer path 382 between the MSC 124 and the PSTN 132 that was previously used to carry the call that was being carried in the circuit network is still in use.
[0051]
A control path 470 extends from wireless terminal 140d to GGSN 148 and to MG 150. Additional control paths 472, 474 extend from GGSN 148 to CSCF 152. A control path 478 extends from MG 150 to MGCF / T-SGW 154. A control path 476 links the CSCF and MGCF / T-SGW. All the control paths are packet paths. For example, a line control path 480 implemented as an ITU-T signaling No. 7 link extends from the MGCF / T-SGW 154 to the MSC 124 of the line radio system 120. The line control path 372 extending from the MSC 124 to the PSTN 132 remains in place. Thus, MSC 124 (or another anchor MSC, if present) serves as an anchor MSC for calls that are widely handled by packet network 110.
[0052]
5, 6, and 9 are directed to a call handover from the packet system 110 to the line system 120 with the landside termination passing through a packet network such as PDN 136. Therefore, this handover situation considers a case where a stable call is established between the wireless subscriber terminal 140e and the landside subscriber terminal 138 through the circuit radio system 120 and the packet landside network PDN 136.
[0053]
In order to perform a handover, a stable call must be established from wireless terminal 140e to landside terminal 138. The configuration is best seen in FIG. A control path 570 exists between the terminal 140e and the CSCF 152. An additional control path 572 extends between CSCF 152 and GGSN 148. A further control path 574 extends between the GGSN 148 and the packet landside network PDN 136. All the control paths are packets. A packet bearer path 580 extends between the terminal 140e and the GGSN 148. A packet bearer path 582 extends between the GGSN 148 and the packet land side network PDN 136.
[0054]
FIG. 9 is a diagram illustrating a case where a handover is performed from the packet system 110 to the line system 120 in the case of a call between the wireless terminal 140 and the landside packet terminal 138, which is used in conjunction with the cooperative wireless network 100 of FIG. 7 is a flow diagram illustrating a method 900 according to an aspect of the invention. The method begins at step 910 where the packet system 110 determines that a handover is required and the acceptable handover target is a base station 122 in the circuit system 120. See also the description of the handover decision associated with step 710. This determination can be made, for example, by the BSS 142 and reported to the CSCF 152. In step 912, the CSCF 152 recognizes that the handover target is in the circuit radio system 120.
[0055]
In step 914, CSCF 152 and MGCF / T-SGW 154 establish bearer paths 682 and 684 to MG 150 and direct the call to MSC 124 of circuit system 120 and perform the necessary bearer content conversion. In step 916, MGCF / T-SGW 154 negotiates a handover with system 120 by formatting and initiating an appropriate handover message sequence exchange with system 120. If the system 120 uses the ANSI-41 inter-system operation protocol, the handover negotiation may employ the message sequence described with step 714. In step 918, the packet system 110 instructs the wireless terminal to begin using the allocated traffic channel of the circuit system 120. The wireless terminal executes the above command. In step 920, the MSC 124 notifies the MGCF / T-SGW 154 that the radio terminal 140f (see FIG. 6) has been successfully handed over to the circuit system 120. In step 922, resources used by the call in the packet system 110 are released to the extent necessary to support the connection between the MSC 124 of the circuit network and the landside network PDN 136. Bearer path 582 between GGSN 148 and PDN 136 is still in use. The method ends at step 924.
[0056]
FIG. 6 is a block diagram showing the final configuration of the control path and the bearer path when the handover from the packet system 110 to the circuit system 120 is successfully completed. A bearer path 680 extends from the wireless terminal 140f through the BSS 122 to the MSC 124. Further, a bearer path 682 extends from the MSC 124 to the MG 150 of the packet system 110. A bearer path 684 further extends from MG 150 to GGSN 148. When the call is carried in the packet network, the bearer path 582 between the GGSN 148 and the PDN 136 that was previously used to carry the call is still in use. A control path 670 extends from the wireless terminal 140f to the MSC 124. A control path 672 extends from the MSC 124 to the MGCF / T-SGW 154 of the packet radio system 110. Further control paths 674, 676, and 678 link MG 150 to MGCF / T-SGW 154, MGCF / T-SGW 154 to CSCF 152, and CSCF 152 to GGSN 148, respectively. The packet signaling control path 574 from the GGSN 148 to the PDN 136 remains in place. Therefore, the MGCF / T-SGW 154 and the MG 150 cooperate to perform the function of the anchor MSC for calls that are currently widely processed by the circuit system 120.
[0057]
In this specification, the packet radio system 110 and the line radio system 120 are described as separate radio systems, and each system is implemented using elements that are different from those used to implement the other system for simplicity. Although shown in the accompanying drawings as being shown, it will be appreciated that in some embodiments, wireless systems 110 and 120 may actually be implemented using common elements and components. Thus, in practice, a single component or element may perform selected functions of both wireless systems 110 and 120, and may consolidate multiple components, elements, and functions into a single unit. . By way of example, and not limitation, a single base station system (which may comprise shared control and radio elements) may perform the functions of both packet BSS 142 and circuit BSS 122, and the base station system may be configured as SGSN 146. And a connection to both the MSC 124. Similarly, a single unit may perform the functions of packets SGSN 146, GGSN 148, CSCF 152, MGCF / T-SGW 154, and line MSC 124. In such a case, and particularly when various components are provided by the same vendor, the inter-system interaction protocol used between these systems is not a standard protocol such as ANSI-41 but a form of a message protocol defined by the vendor. Can take. However, it is still necessary to implement both the packet call model and the line call model described above and perform a handover between them.
[0058]
The present application relates to communication systems including multimedia communication systems. The communication system includes analog electronic systems, digital electronic systems, microprocessors, and other processing elements, and software and other embodied steps that implement methods, processes, or policies in combination with such systems and processing elements, It can be implemented using various electronic and optical technologies, including but not limited to a collection of instructions and the like. The embodiments described herein are exemplary. Thus, although the embodiments have been described with reference to particular techniques, it will be appreciated that other equivalent techniques may be used to implement the system in the spirit of the invention.
[0059]
In accordance with aspects of the present invention, an improved wireless network and associated method for providing inter-system handoff between an existing circuit radio system and a packet system is disclosed. The packet radio system advantageously converts between the line call model and the packet call model and also converts bearer traffic between the formats required by the line system and the packet system. The media gateway component performs bearer traffic conversion between formats used in each system. When the media gateway, the media gateway control function, and the related call state control function cooperate to emulate the behavior of the circuit radio system, the packet system is separated from another circuit radio system when incorporated in the conventional circuit system. looks like. If necessary, the media gateway, media gateway control function, and call state control function further cooperate to emulate the function of the anchor MSC of the circuit radio system. With the improved network and method, a handover can be performed between the line system and the packet system while minimizing or avoiding changes to the conventional wireless system.
[0060]
The above-described embodiments of the present invention are merely examples of how the present invention may be implemented. Other methods are possible and are within the scope of the appended claims which define the invention.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a collaborative radio network 100 constructed in accordance with an aspect of the present invention, including a packet radio system and a line radio system configured for inter-system operation, wherein a radio terminal and a landside 3 further shows the control before the handover from the packet system to the line system and the initial configuration of the bearer signal path in the case of a call between line terminals.
2 is a block diagram of the cooperative wireless network 100 of FIG. 1, showing the final configuration of control and bearer signal paths in the result of a handover from the packet system to the line system in the case of the call of FIG. ing.
3 is a block diagram of the collaborative wireless network 100 of FIG. 1, showing control and bearer signal paths prior to handover from a line system to a packet system in the case of a call between a wireless terminal and a landside line terminal. The initial configuration is shown.
4 is a block diagram of the cooperative wireless network 100 of FIG. 1, showing the final configuration of control and bearer signal paths in the result of a handover from the circuit system to the packet system in the case of the call of FIG. 3; ing.
FIG. 5 is a block diagram of the collaborative wireless network 100 of FIG. 1, showing control and bearer signal path before handover from the packet system to the circuit system in the case of a call between the wireless terminal and the landside packet terminal; The initial configuration is shown.
6 is a block diagram of the collaborative wireless network 100 of FIG. 1, showing the final configuration of control and bearer signal paths in the result of a handover from the packet system to the circuit system in the case of the call of FIG. ing.
7 is an aspect of the present invention used in combination with the cooperative wireless network 100 shown in FIG. 1 for performing handover from a packet system to a line system in the case of a call between a wireless terminal and a landside line terminal. FIG.
8 shows an aspect of the present invention used in combination with the cooperative wireless network 100 shown in FIG. 1 for performing a handover from a line system to a packet system in the case of a call between a wireless terminal and a landside line terminal. FIG.
9 is an aspect of the present invention used in combination with the cooperative wireless network 100 shown in FIG. 1 for performing handover from a packet system to a circuit system in the case of a call between a wireless terminal and a landside packet terminal. FIG.

Claims (10)

Used in conjunction with the first wireless system employing packet technology with the radio communications with the terminal, a wireless communication network and a second wireless system using a non-linear line technology for communication with the terminal, the terminal and call handover you involved different endpoint a row cormorants method, the call is first using the first wireless system, and are transferred to the use of the second wireless system, said method But,
Transmitting a handover request for the call from the first wireless system to the second wireless system ;
Emulating the behavior of a handover management component of the second radio system for the first radio system , wherein the emulation is performed in the first radio system using packet technology, The method is further
Through said second wireless system, and providing a path for bearer traffic between the endpoint and the terminal, method. A first wireless system using a line technology with a wireless communication with the terminal, used in conjunction with a wireless communication network and a second wireless system employing packet technology for wireless communications with said terminal, said terminal and another a call handover endpoint you involved row cormorants method, the call is first using the first wireless system, and are transferred to the use of the second wireless system, the method comprising:
Sending a handover request for the previous logger from the first wireless system to the second radio system,
A step of emulating a message in accordance with defined intersystem operations protocol comprises sending to the first wireless system, the behavior of a handover management component of the second radio system said first radio system,
Through said second wireless system, and providing a path for bearer traffic between the endpoint and the terminal, method. Steps to the emulated according stipulated systems between operating protocol, steps including receiving a message from the sending to the second wireless system or said second wireless system, the method of claim 1, wherein . Step may including the step of emulating the behavior of the mobile switching center in a circuit wireless system, the method of claim 1 wherein said emulating. The first including the step of converting the call state information between a call model used by the call model and the second radio system used in a wireless system, the method of claim 2 wherein. The first step of including converting the control messages between the format used in the wireless system with the format used in the second wireless system, method of claim 2 wherein. 3. The method of claim 2, comprising converting bearer traffic between a format used in the second wireless system and a format used in a network associated with the endpoint. The first wireless system includes a Ruge Towei to convert bearer traffic between a form used by said first and is that form used in the wireless system a second wireless system, the method comprising:
Wherein through the second wireless system and the gateway, step a including establishing a bearer path to said endpoint method of claim 1. A wireless communication network having a first wireless system employing packet technology with the wireless communication with the end-terminal and a second wireless system using a line technology with the wireless communication with the terminal, the wireless communication network Supports handover of calls involving the terminal and another endpoint, the call being initially transferred using the first radio system and then using the second radio system, the radio Communication network
Means for transmitting a handover request for the call from the first radio system to the second radio system;
The behavior of the handover management component of the second radio system and a emulated to Ruha command off manager means for said first radio system, the emulated first wireless using packet technology Performed in a system, the network further comprising:
A wireless communication network comprising means for providing a path for bearer traffic between the terminal and the endpoint through the second wireless system. A wireless communication network comprising: a first wireless system that uses line technology for wireless communication with a terminal; and a second wireless system that uses packet technology for wireless communication with the terminal, wherein the wireless communication network includes: Supporting call handover involving a terminal and another endpoint, wherein the call is initially used to use the first radio system and is forwarded to use the second radio system; ,
Means for transmitting a handover request for the call from the first radio system to the second radio system;
Handoff manager means for emulating the behavior of the handover management component of the first radio system in the second radio system, comprising sending a message to the first radio system according to a defined intersystem operating protocol;
Means for providing a path for bearer traffic between the terminal and the end point through the second wireless system .

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